"Loving" is certainly the most appropriate word to describe the relationship between the speaker and her husband. The speaker is trying to infer that her marriage is wonderful and special. There is an equal balance of love between husband and wife. That balance is expressed in the poem in content and in form. 

If ever two were one, then surely we. 

If ever man were loved by wife, then thee;

If ever wife was happy in a man,

Compare with me, ye women, if you can. 

She loves her husband as sure as any woman loves a husband and she boasts that he makes her happier than any other man could. Also note the repetition of "ever" because this sets up the conclusion of the poem where the speaker suggests that their love is eternal. 

Then while we live, in love let's so persevere

That when we live no more, we may live ever. 

So, "eternal" is another word appropriate to the speaker's feelings about her love for (and from) her husband. Also note the balance in the last two lines: just as they share and express their love during their lives, that love will continue to exist after they've died and/or in heaven. Although not a particularly romantic word, "balance" would be useful in describing their love because it is equally given from both husband and wife. And in the last lines, more balance as their love exists on two planes: during life and following death. Also consider the word "ineffable" which means too good to be described in words. Her love for her husband is ineffable (although she certainly uses words, the poem itself, to describe it). But she remarks how her love and her husband's love for her can not be qualified: "My love is such that rivers cannot quench, / Thy love is such I can no way repay."